1. Field of the Invention
The present invention relates to a drive mechanism, which is capable of pressing a workpiece by displacement of a displacement member under a driving action of a rotary drive source, and to a gripper mechanism equipped with such a drive mechanism.
2. Description of the Related Art
Heretofore, a drive mechanism has been used for pressing a workpiece by means of a displacement member, which is displaced under a driving action of a rotary drive source such as a motor or the like. For example, an electrical gripper (electrical chuck) for gripping various components or the like (workpieces) is known, the electrical gripper being attached to an end of a shaft or the like of a working machine, wherein an opening/closing operation of openable/closable gripper members is carried out using a drive force of the motor to grip the workpieces.
As such an electrical gripper, in Japanese Laid-Open Patent Publication No. 08-150531, a structure is disclosed in which a master jaw constituting a gripper section is driven by transmittal of a rotary drive force of a motor, whereupon a workpiece is gripped between the master jaw and a soft jaw.
However, generally, at times of emergency power stoppage, or when electrical power is interrupted, the generated force (drive torque) is lost, unless electrical energy is stored. As a result, it is necessary to perform continuous energizing of the gripper after the workpiece has been gripped by the gripper for maintaining the gripped state, and thus, the longer the retaining time is sustained, the more the electrical energy is consumed. On the other hand, when electrical power to the motor is stopped in a state where the workpiece is gripped, there is a potential for the workpiece to be dropped from the gripper.